In a case that a pixel shape in a luma domain is not similar to a pixel shape in a chroma domain in an input image, a prediction image that is generated in the reuse of a luma prediction mode is made more accurate.A moving image decoding apparatus 1 includes a gradient deriving unit 1453B that references a chroma gradient definition DEFANG1C, and derives a chroma prediction direction from a prediction mode based on a luma prediction direction.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An image decoding apparatus for decoding an image by generating prediction images using by an intra prediction mode, the image decoding apparatus comprising: a circuit; wherein the circuit is configured to derive a chroma prediction mode based on a luma prediction mode; and the circuit is configured to generate a chroma prediction image by the chroma prediction mode, wherein the circuit is configured to derive, in a case that a chroma prediction mode index included in coded data is one: (i) the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and (ii) the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
2. The image decoding apparatus according to claim 1 , wherein the chroma prediction mode is derived in a case that a color format is a 4:2:2 format.
3. An image decoding method for decoding an image by generating prediction images using by an intra prediction mode, the image decoding method comprising the steps of: (a) deriving a chroma prediction mode based on a luma prediction mode; and (b) generating a chroma prediction image by the chroma prediction mode, in the step (a), in a case that a chroma prediction mode index included in coded data is one: (i) deriving the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and (ii) deriving the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
4. The image decoding method according to claim 3 , wherein the chroma prediction mode is derived in a case that a color format is a 4:2:2 format.
5. An image coding apparatus for coding an image by generating prediction images using by an intra prediction mode, the image coding apparatus comprising: a circuit; wherein the circuit is configured to derive a chroma prediction mode based on a luma prediction mode; and the circuit is configured to generate a chroma prediction image by the chroma prediction mode, wherein the circuit is configured to derive, in a case that a chroma prediction mode index is one: (i) the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and (ii) the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
6. The image coding apparatus according to claim 5 , wherein the chroma prediction mode is derived in a case that a color format is a 4:2:2 format.
7. An image coding method for coding an image by generating prediction images using by an intra prediction mode, the image coding method comprising the steps of: (a) deriving a chroma prediction mode based on a luma prediction mode; and (b) generating a chroma prediction image by the chroma prediction mode, in the step (a), in a case that a chroma prediction mode index is one: (i) deriving the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and (ii) deriving the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
8. The image coding method according to claim 7 , wherein the chroma prediction mode is derived in a case that a color format is a 4:2:2 format.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 7, 2017
October 17, 2017
Browse 5M+ US patents with plain-English claim translations and AI-generated analysis.